Refrigerator plant



Dec. 1, 1931.) E. e. ROWLEDGE REFRIGERATOR PLANT Filed May 19, 1930 2 Sheets-Sheet 1 Dec. 1, 1931. E. G. ROWLEDGE REFRIGERATOR PLANT Filed May 19, 1950 '2 Sheets-Sheet 2 Patented Dec. 1, 1931 UNITED STATES PATENT OFFICE ERIC GEORGE ROWLEDGE, OF NEW ELTHAM, LONDON, ENGLAND, ASSIGNOR TO J. STONE & COMPANY LIMITED, OF DEPTFORD, ENGLAND, A CORPORATION OF GREAT BRITAIN REFRIGERATOR PLANT -Application filed May 19, 1930, Serial No. 453,825, and in Great Britain June 19, 1929.

This invention concerns improvements in and connected with refrigerating plants, particularly for use on vehicles such as railway carriages and wagons.

The object of the invention is to overcome certain defects to which existing plants may be liable and to improve the operation of said plants without the aid of auxiliary apparatus the use of which in railway vehicles for instance, may be inconvenient, or impossible.

The type of refrigerating plant to which the invention is applicable includes an evaporator which is generally associated with cold storage means such as drums containing brine. The evaporator lies in a pipe line connected up to the suction and delivery sides of a compressor and the refrigerant supplied to said evaporator is controlled by an automatic regulating valve sometimes termed a load demand valve. Now owing to the characteristics of such valves it may be possible, after the refrigerating plant or compressor has ceased to run, for liquid refrigerant to pass from the condensing or high pressure side of the plant to the evaporating or low pressure side thereof. The volumetric capacity of the evaporator is often insulficient to contain all this-liquid refrigerant and trouble may be experienced 011 this account. Thus in installations where the compressor is at a lower level than the evaporator, liquid refrigerant may find its way back into the compressor crankcase, resulting in the pos sibility of serious liquid hammer which is detrimental to the eflicient operation and reliability of the plant and of the compressor in particular. Such installations may be fitted with electrically operated valves for shutting off the liquid but this provision is not always feasible, even where desirable; this is the case, for example, with refrigerated railway wagons or other refrigerator installations in which electricity is not available.

According to the present invention, in ordcr to obtain efiicient control of the refrigerant. without such means as electrically actuated stop valves provision is made for trapping or collecting refrigerant. preferably at or in the vicinity of the evaporator. during the time that conditions such as those referred to above might arise, that is more particularly when the plant is not running. To effect this trapping or collecting of the refrigerant provision may be made in the evaporator or evaporator line of an accumulator vessel or vessels which while of sufficient capacity to hold the whole charge of refrigerant, will not affect in any way the proper operation of the evaporator or the regulating valve.

One example of. refrigerating plant incorporating an arrangement of this kind will now be explained by reference to the accompanying drawings. While the particular plant described is more particularly applicable to a railway vehicle installation it will be appreciated that it could be readily adapted for other purposes. In said draw- 1ngs:

Figure 1 is a plan view, partly sectioned, of the evaporator,

Figure 2 an elevation thereof,

Figure 3 a flow diagram and Figure at an axial section of a load demand valve.

In essentials such a plant will comprise as usual a compressor 1, a condenser 2, a loaddemand regulating valve 3 and an evaporator arrangement 4 (Figure 3). The load demand valve 3 which, as already mentioned, automatically controls the supply of liquid refrigerant to the evaporator 4. to suit the working conditions consists essentially of two parts, a thermostatic device in the return vapour line 5, i. e. on the suction side of the compressor 1, and associated therewith a valve arrangement in the liquid refrigerant supply line 6 on the delivery side of the condenser 2 and compressor 1. The thermostatic device may advantageously consist as shown in Figure 4 of a copper bellows-type thermostat 7 arranged to be operated by the combined effects of the pressure and temperature of the vapour drawn past it through the return line 5 from the evaporator 4 to the compressor 1. The valve means proper, may be an expansion valve arrangement comprising two valves 8. 9 in tandem, separated from the thermostat 7 in a liquid and vapour tight fashion by a thin steel diaphragm 10,

mounted in the top plate of the thermostat bellows 7. The valve arrangen'lent is also subject to the influence of a spring 12 tending to keep the upper valve 9 closed. The force exerted by the spring 12 is adjustable by screw-means 13 for a purpose to be explained.

Shortly this valve arrangement will operate as follows :As the vapour from the evaporator 4 fiows over the corrugated sur-.

face of the bellows thermostat 7, the vapour contents of the thermostat is influenced by changes of temperature of the returning vapour and tends to expand or contract therewith. If, the liquid refrigerant supplied to the evaporator 4 is in excess of that required, the surplus will be drawn back towards the compressor 1 and the returning vapour will be wet, that is, will contain a proportion of liquid in suspension Such liquid in the return vapour comes into contact with the thermostat 7 which contracts owing to the lowering of the temperature, enabling the spring 12 to close the valve 9 and reduce the liquid refrigerant admitted to the evaporator 4. Should the return vapour pass the bellows 7 in a superheated-state, it will cause the temperature to rise andthe expanding bellows will open the valves 8 and 9 to admit more liquid to the evaporator 4.

It will be seen, therefore, that the valve 3 is intended to allow just as much liquid refrigerant to pass into the evaporator 4 as can be evaporated, irrespective of the temperature conditions inside or outside said evaporator, the object being to maintain constant the quality of the return vapour, or in other words to maintain a definite but adj ustable superheat. Adjustment of the spring 12 referred to adjusts the superheat of the return gas by modifying the operation of the valve 9.

The form of evaporator illustrated is suitable for a refrigerated railway vehicle or other cold room and comprises a series of drums 14 each containing a cold-accumulating fluid such as brine through which passes an evaporator pipe 15 fitted with annular fins 16 to increase the surface area.

15 communicate with the vapour return line 5 by branch pipes 19. The intermediate evaporator pipes 15 are connected in series by communication pipes 20 at alternate ends thereof.

The liquid trapping or collecting means in the arrangement illustrated are disposed at the ends of the lowest evaporator pipes 15 remote from the connection 18 to the liquid refrigerant supply line 6 and each consists essentially of an accumulating vessel in the form of a vertical cylinder 21 connected by a pipe 22 from its upper part with the lowest evaporator pipe 15 of the set and by a pipe 23, extending axially down into it to within a fraction of an inch from its bottom, with the second lowest evaporator pipe 15. The accumulator capacity should be such as to hold something more than the total charge of refrigerant. Where, as shown, two sets 17 of evaporator tubes 15 are connected in pal-al lel to common supply and return lines 5, (3, one accumulator 21 is preferably provided in each set.

The operation of the accumulators 21 is as follows :Let it be assumed that after such a refrigerating plant has been in operation for some time and the brine in the drums 14 around the evaporator pipes 15 has been cooled down to a low temperature, the compressor is shut down, say automatically by a thermostat in a cold room or by the train stopping in the case of a railway vehicle with axle driven refrigerator compressors. In such circumstances, due to the characteristics of the valve arrangement 3 described above, liquid refrigerant will continue to flow into the evaporator pipes 15 where it will collect in the accumulators 21, as the compressor 1 is not operative. The temperature in the two lowest evaporator pipes 15 of each set 17 being substantially equal there will be a hydrostatic balance between them and no tendency or pressure to cause the liquid refrigerant to flow up the pipe 23 from the accumulator cylinder 21. into and through the second evaporator pipe 15 and on towards the compressor 1.

When the compressor is started up, however, liquid refrigerant will flow from the accumulators 21 in such quantities as can be evaporated in the evaporator pipes 15 following said accumulators. Again owing to the characteristics of the valve 5, however, no further liquid refrigerant will be admitted until the accumulators are emptied or almost emptied. Normal working will then automatically recommence. It will be appreciated, therefore, that the normal functioning of the installation is not interfered with while defects of existing plant are overcome.

I claim 1. Refrigerating plant comprising a compressor, a condenser, an evaporator consisting of a plurality of evaporator elements at a higher level than said compressor, a load demand valve controlling the supply of refrigerant and a trap-vessel connected between two of said evaporator elements and capable of containing at least the total charge of liquid refrigerant.

2. Refrigerating plant comprising a conr pressor, a condenser, a series of evaporator pipes at a higher level than the compressor, a load demand valve, an accumulator vessel arranged between two of the extreme pipes of the series at the end thereof nearest the condenser, a connection between the first in order of said two pipes and said vessel and a rising connection between said vessel and the second of said pipes, said vessel and rising connection forming a liquid trap when the compressor is not working.

3. Refrigerating plant comprisinga compressor, a condenser, a series or evaporator pipes, a load demand valve, an accumulator vessel, a connection between the upper part of said vessel and one end of the extreme evaporator pipe of the series, the other end thereof being connected to the condenser, a stand pipe of which the open lower end extends down inside the vessel almost to the bottom thereof, and a connection between the upper end of said pipe and the next evaporator pipe of the series.

ERIC GEORGE ROWLEDGE, 

